PO 8500 Rubber on Seamaster 300?

Hey all - I'm in the process of purchasing a blue Seamaster 300 and deciding between the bracelet and rubber strap. I already have a Planet Ocean 8500 from ~2012 and purchased the blue rubber with white stitching / deployment clasp. The rubber is 20mm (same as the 300) but it's curved. Does anyone know if it will fit on the 300 Seamaster? If so, there's no reason to even consider purchasing the 300 on the rubber. Thanks in advance!